extension **
telephone extension
extension phone

"Take that extension phone on the table and listen in."

"Suppose I put him on the extension phone for a three-way talk."

On some models this feature works with any extension phone.

I was just about asleep when the extension phone rang.

He sat, finally, at a table on which rested an extension phone.

Keen rolled over, reached for an extension phone and answered.

She nodded to Mason, who picked up the extension phone on his desk.

In the downstairs entry, he heard her pause and dial the extension phone.

Close by, on the coffee table, is a remote control for the TV and an extension phone.

Nine billion calculations a second, and these guys don't have an extension phone.